Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 50: Poster II

HL 50.45: Poster

Thursday, March 30, 2006, 16:30–19:00, P3

Solution processed single crystal organic field-effect transistors based on tetrathiafulvalene derivates — •M. Leufgen¹, O. Rost¹, G. Schmidt¹, N. S. Oxtoby², M. Mas-Torrent², N. Crivillers², J. Veciana², C. Rovira², J. Geurts¹, and L. W. Molenkamp¹ — ¹Universität Würzburg, Physikalisches Institut (EPIII), Am Hubland, D-97074 Würzburg, Germany — ²Institut de Ciencia de Materials de Barcelona(CSIS), Campus UAB, 08193 Cerdanyola, Spain

Solution processed tetrathiafulvalene (TTF) derivates as active materials in organic field effect transistors (OFETs) are electrically analysed. Dithiophene- and dibenzo-tetrathiafulvalene (DT- and DB-TTF) are drop cast from solution of toluene onto lithographically structured bottom contact FET-templates with common gate and SiO₂ dielectric. They crystallise in several micrometer size single crystals in an elongated evaporation process. A limited number of crystals hits the electrodes and thus constitutes the active channel. Here, the channel length is varied from 100 µm into the sub-micrometer regime (< 100 nm), with the use of 100 (20) nm thick SiO₂ in the first (second) case. The characteristics show the excellent properties of the materials with an on/off-ratio exceeding 10⁶ and mobility values as high as 3 cm²/Vs (in the case of DT-TTF), which is among the highest reported for solution processed crystals. The general scaling behaviour is a decrease in mobility from the 10⁰ to the 10⁻¹ cm²/Vs order of magnitude, when going to sub-micrometer channel length, due to an influence of the contact resistance. The results on temperature dependant behaviour prove a thermally activated transport.